Cytotoxicity of the Vibrio vulnificus MARTX toxin effector DUF5 is linked to the C2A subdomain

Proteins. 2014 Oct;82(10):2643-56. doi: 10.1002/prot.24628. Epub 2014 Jun 26.


The multifunctional-autoprocessing repeats-in-toxin (MARTX) toxins are bacterial protein toxins that serve as delivery platforms for cytotoxic effector domains. The domain of unknown function in position 5 (DUF5) effector domain is present in at least six different species' MARTX toxins and as a hypothetical protein in Photorhabdus spp. Its presence increases the potency of the Vibrio vulnificus MARTX toxin in mouse virulence studies, indicating DUF5 directly contributes to pathogenesis. In this work, DUF5 is shown to be cytotoxic when transiently expressed in HeLa cells. DUF5 localized to the plasma membrane dependent upon its C1 domain and the cells become rounded dependent upon its C2 domain. Both full-length DUF5 and the C2 domain caused growth inhibition when expressed in Saccharomyces cerevisiae. A structural model of DUF5 was generated based on the structure of Pasteurella multocida toxin facilitating localization of the cytotoxic activity to a 186 amino acid subdomain termed C2A. Within this subdomain, an alanine scanning mutagenesis revealed aspartate-3721 and arginine-3841 as residues critical for cytotoxicity. These residues were also essential for HeLa cell intoxication when purified DUF5 fused to anthrax toxin lethal factor was delivered cytosolically. Thermal shift experiments indicated that these conserved residues are important to maintain protein structure, rather than for catalysis. The Aeromonas hydrophila MARTX toxin DUF5(Ah) domain was also cytotoxic, while the weakly conserved C1-C2 domains from P. multocida toxin were not. Overall, this study is the first demonstration that DUF5 as found in MARTX toxins has cytotoxic activity that depends on conserved residues in the C2A subdomain.

Keywords: MARTX; Vibrio vulnificus; cytotoxin; effector domains; yeast screen.

Publication types

  • Comparative Study
  • Research Support, N.I.H., Extramural

MeSH terms

  • Aeromonas hydrophila / metabolism
  • Antibiotics, Antineoplastic / chemistry
  • Antibiotics, Antineoplastic / metabolism
  • Antibiotics, Antineoplastic / pharmacology*
  • Bacterial Toxins / chemistry
  • Bacterial Toxins / genetics
  • Bacterial Toxins / metabolism
  • Bacterial Toxins / pharmacology*
  • Cell Shape / drug effects
  • Female
  • HeLa Cells
  • Humans
  • Models, Molecular*
  • Mutant Proteins / chemistry
  • Mutant Proteins / metabolism
  • Mutant Proteins / pharmacology
  • Pasteurella multocida / metabolism
  • Peptide Fragments / chemistry
  • Peptide Fragments / genetics
  • Peptide Fragments / metabolism
  • Peptide Fragments / pharmacology*
  • Photorhabdus / metabolism
  • Protein Conformation
  • Protein Interaction Domains and Motifs
  • Protein Stability
  • Protein Transport / drug effects
  • Recombinant Fusion Proteins / chemistry
  • Recombinant Fusion Proteins / metabolism
  • Recombinant Fusion Proteins / pharmacology
  • Recombinant Proteins / chemistry
  • Recombinant Proteins / metabolism
  • Recombinant Proteins / pharmacology
  • Saccharomyces cerevisiae / growth & development
  • Saccharomyces cerevisiae / metabolism
  • Uterine Cervical Neoplasms / drug therapy*
  • Uterine Cervical Neoplasms / metabolism
  • Uterine Cervical Neoplasms / pathology
  • Vibrio vulnificus / metabolism*


  • Antibiotics, Antineoplastic
  • Bacterial Toxins
  • Mutant Proteins
  • Peptide Fragments
  • Recombinant Fusion Proteins
  • Recombinant Proteins